Reported by @voodoos

After running opam pin dune --dev-repo ... when I print the version of Dune it says: 3.12.0-2842-g6b7bdfe

This messes up with vscode detection of pkg features that relies on the version number being >= to 3.20

@voodoos also identified the source of the problem, which is that installing from source in this way, dune uses git describe at https://github.com/ocaml/dune/blob/main/boot/duneboot.ml#L1240-L1241

and since the current release process is not tagging main, this produces a misleading version.

It would be better that we do not include a version string at all, if we cannot print something accurate. However, moving the release process to use trunk based development should help alleviate a chunk of this pain.

An alternative is that we record the current version number in a file in the repo, and increment it as part of the release process. This is not an uncommon practice and I've had it work well in the past.